NASA Lucy Mission Discovers Wobbling Peanut-Shaped Asteroid Donaldjohanson

NASA's Lucy spacecraft has returned unprecedented data revealing that the asteroid named Donaldjohanson possesses a distinct peanut-like shape and an irregular, two-axis rotation. Unlike most asteroids that spin smoothly on a single axis, Donaldjohanson exhibits a wobbling motion. Data captured during a 960-kilometre flyby in April 2025 also identified signatures of iron-rich clay minerals, suggesting that this object was once exposed to liquid water for an extended period while part of a larger parent body.

Researchers attribute the asteroid's unusual rotation to the YORP effect, a phenomenon where uneven solar heating causes infrared radiation to emit from the surface, creating a subtle recoil force. Because the asteroid’s peanut shape is asymmetric, these forces produce a net torque, causing the rotation to change and the object to wobble. This discovery mirrors observations made on other asteroids such as Bennu and Ryugu, which also contain magnesium-rich clays, reinforcing the theory that these objects originated from larger bodies where water-mineral interactions lasted millions of years.

The findings provide a new window into the early history of the solar system, specifically regarding the role of water in the evolution of small bodies. Named after the discoverer of the fossilized 'Lucy' skeleton, the Donaldjohanson asteroid was formed roughly 155 million years ago following a massive collision in the main belt between Mars and Jupiter. As the Lucy spacecraft continues its long-term trajectory toward the Jupiter Trojan asteroids, the data collected from this encounter remains a key piece of evidence for understanding the chemical and physical composition of the early solar system.